Vascular endothelial cells line the circulatory system, forming the interface between the blood and the underlying vessel wall and tissue spaces. In this anatomic location, the endothelium serves as the "gateway" to the tissues for blood cells and macromolecules. It is my hypothesis that endothelial cell surface proteins play a role in binding and transendothelial migration of blood elements and further that alterations of endothelial cell surface proteins will produce changes in blood cell adhesion and entrance into the tissue spaces. The proposed research focuses upon endothelial cell surface proteins that are important for interactions with lymphocytes and in the development of a cell-mediated immunological reaction. Proteins known to be involved in T lymphocyte recognition of target tissues, including both major histocompatibility complex (MHC) antigens and non-MHC proteins, will be studied in cultured human vascular endothelial cells by immunochemical, biochemical and molecular biological approaches. The actions of gamma interferon, a T lymphocyte secreted mediator protein, upon cultured human endothelium will also be studied. In previous work, it was found that gamma interferon does in fact modulate the phenotype of cultured endothelial cells, and the extent of interferon-induced changes will now be studied. These experiments will use gamma interferon produced from a recombinant gene and thus free of all other human T cell mediators. Biochemical and immunochemical methods will be used to analyze changes in surface membrane and extracellular matrux (basement membrane) proteins of endothelial cells modulated by gamma interferon. In addition, fluorescence microscopy and fluorescence photobleach recovery methods will be used to study changes in the arrangement of endothelial surface and cytoskeletal proteins induced by gamma interferon. Finally, structural analysis of interferon-responsive proteins of functional importance will be undertaken. The objective of this proposal is to understand the mechanism of vascular endothelial interactions with lymphocytes (and eventually other blood elements) at the level of protein structure. Such an understanding may lead to new therapies in conditions such as autoimmunity, vasculitis, allograft rejection and other "altered" endothelium sequelae including atherosclerosis.